FIELD OF THE INVENTION
The invention relates to a device for regulating the fuel pressure in a high-pressure accumulator, including a controller for a volumetric flow in an inflow to a high-pressure pump connected to the high-pressure accumulator, and a pressure sensor assigned to the high-pressure accumulator and signaling the fuel pressure in the high-pressure accumulator to the controller. The invention also relates to a method for regulating the fuel pressure in a high-pressure accumulator for fuel, which includes supplying fuel to the high-pressure accumulator through a high-pressure pump, discharging fuel from the high-pressure accumulator through an injection system, and regulating the volumetric flow of fuel upstream of the high-pressure pump in a low-pressure region as a function of the pressure in the high-pressure accumulator.
High-pressure accumulators for fuel are used in common-rail injection systems. In that case, fuel is pumped into a high-pressure accumulator by a high-pressure pump, and the fuel is supplied to individual injection nozzles from the high-pressure accumulator. That makes it possible to have a high injection pressure which reduces the emission of particles, particularly in diesel injection.
Published European Patent Application 0 299 337 A2, corresponding to U.S. Pat. No. 4,884,545, has already disclosed a device for regulating the fuel pressure in a high-pressure accumulator as well as a method for regulating the fuel pressure in a high-pressure accumulator. In that case, fuel is supplied by a pre-feed pump, through a controllable throttle, to a high-pressure pump which pumps the fuel into the high-pressure accumulator at high pressure. The high-pressure accumulator conducts the fuel further to the injection nozzles and has a safety pressure valve which connects the high-pressure accumulator to the fuel tank when the maximum pressure is exceeded. The controllable throttle is activated by a control unit as a function of operating parameters of the internal combustion engine, so that a regulation of volumetric flow is carried out on the low-pressure side.
The disadvantage of the device and the method described in the prior art is that a reduction of pressure in the high-pressure accumulator can take place only relatively slowly, since the controllable throttle cannot be used for pressure reduction.